Bethesda, Md—Psychiatrist and brain imaging researcher Wayne C. Drevets, MD, recalls a patient dealing with breast cancer and unrelated episodes of major depression. The woman found it easier to talk about the cancer because, Drevets said, "with the depression there was nothing tangible to point to or explain to people, even herself."

It turns out that there is something tangible. A decade of unusually collaborative research by Drevets and a number of other researchers dramatically illustrates that chronic major depression is as physical as diabetes or heart disease. Dysfunctional metabolism and blood flow in the brain's emotional centers mark two physical manifestations of the mental disorder. Charted with magnetic resonance imaging and positron emission tomography scans, these findings have been replicated in dozens of studies.